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OSM's Comments for the Draft Proposed Decision and Findings of Compliance For the Mt. Gunnison No. 1 Mine, 1,765 Acre Modification 1. The effects_of subsidence on the surface-water hydrology and ground-water hydrology at the Mt. Gunnison No. 1 mine need to be assessed. This approval will allow mining up to the Minnesota Creek drainage divide. A permit condition should be added that requests wells be installed in all aquifers in the Minnesota Creek drainage, and sampling and water level measurements be started upon approval of this revision. The monitoring is necessary in order to detect unanticipated changes in the hydrologic character of the Minnesota Creek drainage and relate it to mining activities. Quarterly measurements and samples should be taken and analyzed for TDS, sulfates and several other parameters that show the greatest variability between aquifers. It is recommended that this include a series of wells drilled around the subsidence test panels. The well installations would allow a direct cause and effect analysis to be completed for this area. Two wells directly above the panel to be subsided will not give an idea of the lateral extent of the effects. 2. Stabilization of the slide area above the town of Somerset will partially be by a drainage system to reduce pore pressures. Some provision for maintenance after the applicant has completed mining coal must be provided. 3. The document is unclear with respect to subsidence. It is reported that subsidence will likely cause change in water flows, increase infiltration rates, modify seeps and springs, etc. It is also stated that no significant impacts are expected from subsidence. In order to avoid the appearance of a contradiction, some clarification of impacts is necessary. 4. The document is unclear as to what effects to aquatic life can be expected due to changes in the hydrologic regime resulting from subsidence.